No. 4.] SHUFELDT ON THE OSTEOLOGY OF SPEOTYTO. Ill 



above is a roughened surface that is covered by the expanded end of the 

 radius. 



The carpus is composed of the scapho-lunar, os magnum, and cuneiform. 

 The scapho lunar articulates with radius, os magnum, and ulna. The 

 radial articulation is a rather deep and elliptical concave facet, its lower 

 border gliding over the ulna, while the distal end of the radius plays in 

 the concavity. The opposite face of this six-sided little bone is also 

 smooth, and is a nearly flattened surface that articulates with os mag- 

 num. The upper and lower surfaces, as well as the ends, are simply 

 roughened and fashioned to give the proper form to that part of the joint 

 into which it enters, and for the attachment of ligaments. Os mag- 

 num has become coniiuent with the mid-metacarpal, forming its troch- 

 lear surface for articulation with scapho-lunar, cuneiform, and ulna. The 

 cuneiform is an extremely irregularly shaped bone; it appears to be 

 rather the larger of the two free carpals, and is the lower in regard to 

 position. It articulates with ulna and os magnum, simply. Its outer 

 ulnar facet is elliptical and shallow, monopolizing the entire face of the 

 bone j its inner facet is very irregular, being formed so as to accommo- 

 date itself to the ulnar tubercles, with which it articulates. Projecting 

 towards the metacarpus, this little bone has two prongs or limbs, the 

 inner aspect of the extremities of each possessing a subcircular facette 

 that articulates, the outer and shorter limb with the internal trochlear 

 margin of os magnum, on the same side; the inner and longer limb strad- 

 dles the metacarpal and glides over a surface, during movements of the 

 joint, at a point about where magnum becomess confluent with mid-meta- 

 carpal. The cuneiform has also attached to it ligaments that enclose 

 tbe wrist-joint beneath — capsular ligaments of the carjjus. 



The metacarpus is formed in the usual manner, by the amalgamation of 

 the index, medius, and annularis metacarpals, the first, second, and 

 third, respectively. It is 3.3 centimetres long, articulating with scapho- 

 lunar, ulna, and cuneiform at its proximal extremity by means of os mag- 

 num, that has become anchylosed with mid-metacarpal and the pha- 

 langes at its distal end. The first metacarpal is short, and fused with 

 the second just anterior to the boundary of the trochlear surface of os 

 magnum ; it makes an angle with the shaft of the second metacarpal, 

 its extremity being directed upwards. At its base, close to the shaft of 

 mid-metacarpal, it bears a uniform facette for articulation with the index 

 j)halanx, a free, three-sided, pointed little bone, about 9 millimetres in 

 length. The second metacarpal is straight ; its enlarged proximal ex- 

 tremity is formed chiefly by the confluent os magnum ; its shaft is in- 

 clined to be subtrihedral, with its broadest face looking forwards ; its 

 distal extremity is terminated by a knot-shaped enlargement, that is 

 still further enhanced by the confluence with the third metacarpal. It 

 bears a digit composed of two phalanges, the proximal one bearing on its 

 posterior border, for nearly its entire length, a quadrangular expansion, 

 that has a raised margin, Jeaving a single concavity radiad ; a similar con- 



